This invention relates generally to a copying machine for producing a copy of written or drawn material, and more specifically to a copying machine for reading, and printing copies of a subject copy, written or drawn, by dividing the image of the subject copy into a plurality of picture elements.
A typical copying machine for reading and reproducing a two-dimensional image by dividing the image into a plurality of small picture elements, as represented by the facsimile system, usually reads a subject copy 3 by moving a onedimensional image sensor 2 consisting of a linear array of multiple picture element sensors 1, and prints the image thereof on a copying paper sheet 6 while moving a onedimensional printing head 5 consisting of a linear array of multiple dot printing elements 4, as shown in FIG. 1; or reads the subject copy 3 wrapped around a rotating drum 7 by moving a picture element sensor 1, and prints the image thereof on a copying paper sheet 6 wrapped around a rotating drum 8 while moving a dot printing element 4.
Both conventional types of copying machine are based on the same operating principle that a subject copy is divided into small dots, called picture elements, for reading and reproduction. In both types, the smaller the size of picture elements and the more the total number of picture elements, the better becomes the quality of the reproduced picture. As the total number of picture elements is increased, on the other hand, the time for scanning is increased, resulting in the increased time for completing the reproduction of a subject copy.
A copying machine shown in FIG. 1, which is originally suitable for high-speed copying because of the use of onedimensional picture elements, poses no practical problems at least in terms of copying time. To obtain a high-quality reproduction with this type of copying machine, however, a high-resolution one-dimensional image sensor 2 and a one-dimensional printing head capable of high-density printing are required by increasing the number of picture element sensors 1 and dot printing elements 4 per unit length. This, however, may often result in an expensive copying machine.
A copying machine shown in FIG. 2 can yield a high-quality reproduction by reducing the reading area of the picture element sensors 1 and the printing area of the dot printing elements 4 as well as by reducing the travelling speed thereof to increase scanning density. An increase in total number of picture elements, however, leads to an increase in scanning time and therefore the time for completing the reproduction of a subject copy. In addition, the use of a relatively large rotating drum does not necessarily lend itself to reduction in the size of the copying machine.